Selective excitation of zone-folded phonon modes within one triplet in a semiconductor superlattice

The selective optical excitation of coherent zone-folded acoustic phonon modes in a semiconductor superlattice is demonstrated. By using a time-delayed control pulse, we show the modification of phonon amplitudes within a phonon triplet and demonstrate that the phase relation of phonon modes can be mapped over time delays of several tens of picoseconds. This method with high spectral resolution has the potential to tailor specific amplitudes of phonon modes that are otherwise only collectively excited.